Ohm's Law Calculator
Enter any two known values, voltage, current, resistance, or power, and instantly calculate the other two. Great for electronics projects, troubleshooting, and quick LED resistor sizing.
Calculated from your two known values.
Voltage
12.000 V
Current
2.000 A
Resistance
6.000 Ω
Power
24.000 W
Ohm's Law Formulas
Use the wheel to remember relationships between power, voltage, current, and resistance.
LED Resistor Calculator
Estimate a safe series resistor for a single LED circuit.
Required Resistor
490 Ω
Suggested standard value: 500 Ω
Resistor Power
0.20 W
Choose a resistor with some safety margin.
Common AWG Wire Gauge Reference
Quick reference for typical chassis wiring. Real ampacity depends on insulation, bundle size, temperature, and run length.
| Wire Gauge | Typical Max Current | Common Use |
|---|---|---|
| 24 AWG | 0.58 A | Signals, low-current sensors |
| 22 AWG | 0.92 A | Breadboards, short LED runs |
| 20 AWG | 1.5 A | Control wiring, small loads |
| 18 AWG | 2.3 A | LED strips, automotive accessories |
| 16 AWG | 3.7 A | Low-voltage power, speakers |
| 14 AWG | 5.9 A | 12V circuits, moderate loads |
| 12 AWG | 9.3 A | Higher current DC wiring |
| 10 AWG | 15 A | Inverters, battery leads |
How to Use
- Enter exactly two known values, such as voltage and current or resistance and power.
- Choose the correct unit prefixes, like mA, kΩ, mV, or kW, for each input.
- Review the calculated voltage, current, resistance, and power values instantly.
- Use the LED resistor section to size a series resistor for a simple LED circuit.
- Check the AWG table for a rough wire gauge reference before wiring higher-current circuits.
Frequently Asked Questions
What is Ohm's law?
Ohm's law describes the relationship between voltage, current, and resistance in an electrical circuit. The core formula is V = I × R, where voltage equals current multiplied by resistance.
Can I calculate power with Ohm's law?
Yes. Power can be calculated with P = V × I, P = I² × R, or P = V² ÷ R. Which formula you use depends on the values you already know.
Why does the calculator ask for exactly two values?
Two independent electrical values are enough to solve the other two. Entering more than two can create conflicting inputs, especially if one value was rounded or measured inaccurately.
What does the LED resistor calculator do?
It estimates the resistor needed to limit current through a single LED. You enter the supply voltage, LED forward voltage, and target LED current, and the tool returns the resistor value in ohms.
Are the AWG current ratings exact?
No. They are quick reference values for typical chassis wiring only. Safe current depends on insulation type, ambient temperature, ventilation, cable length, and whether wires are bundled together.